1. Field of the Invention
The present invention relates to a fuel cell system and an activation system thereof for discharging remaining water at an anode side by purging a fuel gas at a stop of a fuel cell.
2. Description of the Related Art
Generally, a fuel cell is configured by comparting a cathode at one side and an anode at the other side with sandwiching a proton conductive polymer electrolyte membrane (PEM) and generates power by an electrochemical reaction of oxygen in the air supplied to the cathode and hydrogen supplied to the anode. And in such a fuel cell system with such the fuel cell, if long time lapses from a power generation stop, there is a problem that: some gas (mainly a nitrogen gas) that does not participate in the power generation stays at the anode side by air invading the anode side through the polymer electrolyte membrane from the cathode side; and it takes time till a restart of the power generation because in such the case a partial pressure of the hydrogen at the anode side is in a state of being lowered in activating a next fuel cell.
As a technology for such the problem is conventionally known one that discharges a nitrogen gas remaining in a flow passage of an anode side by heightening a pressure at the anode side in activating a fuel cell (see paragraphs 0013 to 0017 and FIG. 2 of Japanese Patent Laid-Open Publication Hei. 11-97047). To be more precise, this technology once heightens the pressure at the anode side, then opens a purge valve, and purges the nitrogen gas by supplying a hydrogen gas (fuel gas) to the fuel cell in a state of the purge valve provided at the flow passage of the anode side being closed when activating the fuel cell. In addition, while purging the nitrogen gas, the technology always determines whether or not an output voltage of the fuel cell becomes not less than a predetermined value, and when the output voltage becomes not less than the predetermined value, the technology closes the purge valve and performs a normal power generation (hereinafter the above sequential operation is referred to as “OCV (Open Circuit Voltage) check”. Meanwhile, in the technology, in order to shorten time taken for the OCV check, it is desirable to speedily purge the hydrogen gas remaining at the anode side by heightening the pressure at the anode side higher than in the normal power generation (hereinafter referred to as “first technology”).
In addition, in the fuel cell system, because water is produced by an electrochemical reaction of hydrogen and oxygen, the water stops the fuel cell in a state of the water staying within the system; and then if long time lapses, there is a possibility that the water freezes in winter and a cold district.
As a technology for such the problem is conventionally known one that: a pressure at the anode side is once heightened by closing the purge valve of the anode side without stopping a supply of hydrogen; and then water remaining at the anode side is purged by opening the purge valve (see paragraphs 0009 to 0017 and FIG. 2 of Japanese Patent Laid-Open Publication No. 2002-305017). Meanwhile, in order to prevent a waste of fuel, the technology uses the pressure in the normal power generation and purges the water without heightening the pressure: in the technology it is desirable to open the purge valve as it is, without heightening the pressure when a stop request is output (hereinafter referred to as “second technology”).
However, assuming a case that the first technology and the second technology are combined, because when a stop request is output during an OCV check (to be more precise, after the pressure at the anode side is heightened) in activation, the purge valve is opened as it is, a comparatively large amount of hydrogen should be discharged, and therefore, there occurs a problem that fuel is wasted.
Consequently, it is strongly requested a fuel cell system and an activation method thereof that can suppress an amount of a fuel gas discharged, even when a stop request is output during an OCV check.